The present invention relates to an apparatus for separating oil and contaminants from gas-oil mixtures, and more particularly to a combustion gas-oil contaminant separator for use in internal combustion engines. During operation of an internal combustion engine, combustion gases pass through the small clearance defined between the piston rings and the inner wall of the pistons and enter the crank case. Also engine oil is mixed with the combustion gases by the reciprocation and rotation of the engine components must be separated in order to reduce the comsumption of the engine oil.
Heretofore, there has been proposed a gas-oil separator 8 which is provided in a cylinder-head cover, as shown in FIG. 10. The gas-oil separator 8 has a curved plate 21 which is fixed onto an inner wall 9 of a cylinder-head cover 2. As shown in FIG. 9, the cylinder-head cover 2 has a first extension portion 12 which extends in its longitudinal direction (the direction indicated by the reference Q) and a second extension portion 13 which extends in its lateral direction (the direction indicated by the reference P). The back side portions of the first and second extension portions 12 and 13 are concave, thereby forming a space between the curved plate 21 and the cylinder-head cover 2. This space forms a passage 11 through which blowby gas flows, as shown in FIG. 11. The first extension 12 of the cylinder-head cover 2 forms a part of the passage 11, in which the blowby gas flows in the longitudinal direction of the cylinder-head cover 2 (the direction indicated by the reference Q--Q in FIG. 11). Further, the second extension 13 of the cylinder-head cover 2 forms a part of the passage 11, in which the blowby gas flows in the lateral direction of the cylinder-head cover 2 (the direction indicated by the reference P--P in FIG. 11). The blowby gas enters the passage 11 from an inlet port 15 and exhausts from an outlet port 16. According to the prior cylinder-head cover 2 as shown in FIG. 9, the rigidity of the cylinder-head cover 2 is lowered, particularly in the lateral direction of the cylinder-head cover 2. This is based upon the reason why the first extension portions 12 are provided at both lateral sides of the cylinder-head cover 2. Further, according to the prior cylinder-head cover, the separation between gas and oil is not satisfactory.